We have been cruising with our kids since they were little. I found that you don't need to bring much for entertainment for them as the kids program is awesome and they have lots of toys and activities to keep them busy. Our kids didn't spend alot of time in the kids program but also loved swimming in the pools and exploring the ship with us. I'm sure that you will have a great time. Cruising is a fun family vacation!
I bring small beach toys(pails, shovels) for shore excursions to beaches, an inflatable floating seat for the younger one, sunglasses, books, crayons and paper for the rool and for at dinner, life jacket for smaller kids for pool and shore excursions. Camp Carnival has a lot of stuff for them when they're there.